Hydraulic control device for automatic transmission

ABSTRACT

A hydraulic pressure control device is provided for an automatic transmission including a hydraulic torque-converter or fluid coupling, a change speed gearing, a hydraulic servo for brake bands, clutches and the like. A relay valve is added to a pressure regulator valve for controlling the hydraulic pressure applied to the servo, and in response to the actuation of an automatic shift valve an oil line to the servo is communicated with a pressure control chamber in the pressure regulator valve so that the pressure regulating function of the pressure regulator valve may be varied depending upon the position of a manual valve and also depending upon the actuation of the automatic shift valve. The hydraulic circuit may be simplified.

[56] References Cited United States Patentv 1 1 Kubo 51 Jan. 16, 1973541 HYDRAULIC CONTROL DEVICE FOR AUTOMATIC TRANSMISSION [75] lnventor:Se'itoku Kuho, Toyota, Japan [73] Assignee: Toyota Jidosha KogyoKabushiki ,Kaisha, Toyota-shi, Japan [22] Filed: Feb. 2, 1971 [21] Appl.No.:1l1,978

'[ 30] Foreign Application Priority Data 7 Feb. 3, 1970 Japanm..45/9479v [52] U.S. CL, 74/753, 74/752 A, 74/869 51 1m; (:1. .,...F1'6h3/44,F 16h 5/42,B60k 21/00 [58] Field ofS earch' ..,...74/753,863-865,

UNITED STATES PATENTS 2,995,957 8/1961 Wilson et a1 ..74/752 A 2/1970Ohieet al .74/86 4 12 1970 Kogaki ..74/867 Primary ExaminerArthur T.McKeon Attorney-Cushman, Darby & Cushman [5 7] ABSTRACT A hydraulicpressure control device is provided for an automatic transmissionincluding a hydraulic torqueconverter or fluid coupling, a change speedgearing, a hydraulic servo for brake bands, clutches and the like.

A relay valve is added to a pressure regulator valve for controlling thehydraulic pressure applied to the servo, and in response to theactuation of an automatic shift valve an oil line to the servo iscommunicated with a pressure control chamber in the pressure regulatorvalve so that the pressure regulating function of the pressure regulatorvalve may be varied depending upon the position of a manual valve andalso depending upon the actuation of the automatic shift valve. Thehydraulic circuit may be simplified.

2 Claims; 9 Drawing Figures PATENTEDJAH 16 I975 SHEET 1 [1F 7 INVENTOR AATTORNhYs PATENTEDJAN 15 ms SHEET 2 [1F 7 PREssuRE REGULATOR VALVE.

INVENTOR ATTORNEYS PATENTEDJAH 16 I975 3.710.649

SHEET 3 BF 7 PRESSURE REGULATOR 2'5 SHIFT l VALVE W Q MANUAL V g VALVE/20 /22 L E3 J /2/ [MENTOR 'gf M90 ATTORNEY 3 PATENTED JAN 16 I975 SHEET0F 7 RELAV PzEssu 2e REGULATOR VALVE E VA LV 5 80 /06 2-3 SHBFT VALVEMANUAL.

Y VALVE g /24 i m'guksmm INVENTOR Ollll MUM 2 P [I m 0 GA .I i/ I "1ATTORNEYS PATENTEDJAH 16 I973 SHEET 5 [IF 7 RELAY zsssuze REGULATORVALVE INVENTOR ORNEY PATENTEDJAN 16 I915 3, 710.649-

SHEETBUF'I PRESSURE REGULATOR VALVE 2-5 SHIFT INVENTOR S lfi M L QAWATTORNEYS PATENTEDJAN 16 I973 SHEEI 7 0F 7 PHD IOCOZOOO m 5 w Q mmammmEmz OUTPUT SHAFT REVOLUTION PLL PHL

W Lu m mmbmmmmm $5 ICUO OUTPUT SHAFT REVOLUTION INVENTOR HYDRAULICCONTROL DEVICE FOR AUTOMATIC TRANSMISSION BACKGROUND OF THE INVENTIONThe present invention relates to a hydraulic control device for anautomatic transmission employing a fluid coupling or torque-converter,and more particularly a hydraulic pressure control device forcontrolling the hydraulic pressure (to be referred to as line pressurehereinafter) to be supplied to the hydraulic servos for clutches, brakebands and the like.

SUMMARY OF THE INVENTION I manual valve.

Another object of the present invention is to communicate a linepressure conduit or line through which the line pressure is transmittedto the servos by an automatic shift valve, with a control chamber in thepressure regulator, valve, thereby changing the pressure control orregulating function of the pressure regulator valve depending upon thepresence or absence of the line pressure in said control or regulationchamber in response to the activation or deactivation of the automaticshift valve.

To accomplish the above and other objects of the present invention, inthe D or drive range the hydraulic pressure from an oil pump is directlysupplied into the oil pressure chamber in the pressure adjustment valveso as to oppose the force of a spring loaded at one end of the valvespool of the pressure regulator valve. In the II or second range and Lor low range the hydraulic pressure from the oil pump is slightlyreduced by the relay valve. Thus the function of the pressure regulatorvalve in the. D range is varied from that in the II or L range so thatthe line pressure PL in the II or L range may be higher than the linepressure PL in the D range.

More specifically, a spring is loaded at one end of the valve spool ofthe relay valve and in the D range of the manual valve the hydraulicpressure in a conduit or line selected by the manual valve is directlytransmitted to the chamber of the pressure regulator valve without beingmodified under the force of the spring. In the II and L range, thehydraulic pressure from the oil pump is reduced by a degreecorresponding to the force of the spring before it is transmitted intothe oil pressure chamber in the pressure regulator valve.

Another oil pressure chamber is formed in the pressure regulator valveso that the hydraulic pressure applied to this oil pressure chamberdepending upon the actuation of the automatic shift valvemay oppose theforce of a spring loaded at one end of thevalve spool of the pressureregulator valve. For example in case of a l-2 shift valve, the hydraulicpressure or oil under pres sure is transmitted into the oil pressurechamber when the shift through speeds from the first to the second takesplace, thereby stepping down the high line pressure to the low linepressure.

According to one aspect of the present invention, a hydraulic pressurecontrol device for use in an automatic transmission including afluidtorque-converter or fluid coupling and a transmission provided with ahydraulic servo for brake bands, clutches and the like, comprises an oilpump for generating the hydraulic pressure to be applied to saidhydraulic servo; a pressure regulator valve for controlling thehydraulic pressure to be applied to the hydraulic servo, the pressureregulator valve having an oil pressure chamber formed therein forcontrolling said hydraulic pressure, a

manual valve having at least two positions, a relay valve adapted tosupply a required hydraulic pressure to the oil pressure chamber in thepressure regulator valve, a first conduit for communicating the oil pumpwith the I relay valve when the manual valve is in one position,

and a second conduit for communicating the oil pump with the relay valvethrough the manual valve when the manual valve is in another position,the relay valve having a spring urging its movable valve, the relayvalve supplying a reduced hydraulic pressure to the oil pressure chamberin the pressure regulator valve when the manual valve is in one positionwhich reduced pressure is equal to the hydraulic pressure supplied fromthe first conduit minus the pressure corresponding to the force of thespring, while when the manual valve is in another position the relayvalve supplying the hydraulic pressure supplied from the second conduitand being subjected to no regulation to the oil pressure chamber in thepressure regulator valve, the hydraulic pressure control operation ofthe pressure regulator valve being varied in response to the'positionsof the manual valve.

According to another aspect of the present inven tion, the hydraulicpressure control device further includesa second oil pressure chamberformed in the pressure regulator valve for controlling the hydraulicpressure to be supplied to the hydraulic servo, an automatic shift valveactivated in response to a signal representing a suitable condition foractuating the transmission by supplying to or discharging from thehydraulic servo the hydraulic pressure thereby establishing thelow-speed forward-drive ratio and the high-speed forwarddrive ratio, athird conduit for communicating the conduit for supplying the hydraulicpressure from the automatic shift valve to the hydraulic servo with thesecond oil pressure chamber in the pressure regulator valve and thecontrol operation of the pressure regulator valve being varied inresponse to the position of the manual valve and the actuation of theautomatic shift valve.

BRIEF DESCRIPTION OF THE DRAWING DrangeyFIG. 5, the second in the 11range, no.6, the

first in the L range,and FIG. 7, the second 'in the L range;

FIG. 8 is a graph illustrating the line pressure variation relative tothe rotational speed of the output shaft in the D range, the linepressure being controlled by the hydraulic circuit; and

FIG. 9 is a graph illustrating the line pressure variation relative tothe rotational speed of the output shaft in the II or L range, the linepressure being controlled by the hydraulic circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will bedescribed as being applied to a three-forward-speed andone-reverse-speed automatic transmission, which, as viewed from FIG. 1,consists of a torque-converter unit consisting of a pump 2 directlycoupled to an engine shaft 1, a turbine 3 directly coupled to a turbineshaft 5 and a stator 4, and a planetary gearing together with clutches 6and 7 and brake bands 21 and 22 automatically controlled by a hydraulicservomechanism in a manner well known in the art.

The turbine shaft 5 coupled to the turbine 3 is the input shaft of theplanetary gearing and is splined to a drum 24. The front clutch 6disposed in the drum 24 is engaged or disengaged through a back spring(not shown) by a piston 25 actuated under the hydraulic pressure. Theouter periphery of the drive plate of the front clutch 6 is splined tothe drum 24 while the inner periphery of the clutch disk is splined to ahub 26 which in turn is splined to an intermediate shaft 8. The clutchdisk of the rear clutch 7 is fixed to the front clutch drum 24 while thedrive plate of the rear clutch 7 is splined to the rear clutch drum 27and is adapted to be actuated by a hydraulically actuated piston 28.

An input sun gear is carried by the rear end of the intermediate shaftremote from the hub 26, and a reverse sun gear 10 is carried by the rearclutch drum 27. The inputsun gear 9 is in mesh with the pinions 12 ofaplurality of compound planet pinions 11 while the reverse sun gear 10 isin mesh with an idler gear (See FIG. 2) slidably carried by a pin 14which in turn is fixed to a carrier 13. The idler gear 15 is in meshwith the pinion 16 of the compound planet pinion 11. The pinion 17 ofthe compound planet pinion 11 is in mesh with a gear 19 carried by anoutput shaft 18 of the automatic transmission. The compound planetpinions 11 consisting of the pinions 16, 12 and 17 is carried by thepinion pin 20 which is fixed to the carrier 13.

The carrier 13 has the rear brake band 21 which is applied or releasedso as to lock or unlock the carrier 13. Similarly the rear clutch drum27 has the front brake band 22 for locking or unlocking the rear clutchdrum 27 and thus the reverse sun gear 10.

A one-way brake 23 in the carrier 13 has the same function as that ofthe rear brake band 21 in the low range as will be described in moredetail hereinafter.

Next the mode of operation will be described in brief.

First: Both of the front clutch 6 and the rear brake band 21 areactuated. (However when the power is transmitted from the engine, theone-way brake 23 is actuated thus resulting in the same effect as thatof the rear brake band even when the latter is not actuated, so thatwhen the one-way brake 23 is provided, it is not required to actuate therear brake band 21. However,

the power from the output shaft is not transmitted). In this case, therotation of the turbine shaft 5 is transmitted to the input sun gear 9through the front clutch 6. The carrier 13 is locked by the rear brakeband 21 so that the input rotation is transmitted to the gear 19 carriedby the output shaft through the pinions 12 and 17 from the sun gear 9.In this case, the rotational speed is reduced.

Second: The front clutch 6 is kept actuated while the rear band brake 21is released, but the front brake band 22 is actuated. The turbine shaft5 rotates in unison with the input sun gear 9 while the clutch drum 27and hence the reverse sun gear 10 are locked by the front brake band 22.The rotation of the turbine shaft 5 may be directly transmitted to theinput sun gear 9 which in turn rotates the compound planet pinions 11 inthe direction (counterclockwise direction) opposite to the direction(clockwise direction) of the rotation of the turbine shaft 5. Thereforethe gear 15 tends to rotate in the clockwise direction through thepinion 16, but since the gear 10 in mesh with the idler gear 15 islocked the pinion pin 14 rotates in the clockwise direction. Thisrotation is additionally transmitted to the input shaft gear 19 and tothe input gear 9 which is coupled to the turbine shaft 5. The number ofteeth of the pinion 12 is greater than that of the pinion 17, so thatthe rotational speed of the intermediate shaft 8 becomes higher thanthat of the output shaft 18. In other words, the rotational speed isreduced.

Third: This is obtained by actuating both of the front and rearclutches. Input sun gear 9 rotates in unison with the reverse sun gear10 so that the whole planetary gear set is rotated. In consequence, therotational speed of the output shaft 18 is equal to that of the turbineshaft 5.

Reverse: The rear clutch 7 and the rear brake band 21 are actuated. Thecarrier 13, thus the pinions l4 and 20 are locked so that the rotationof the turbine shaft 5 is transmitted to the reverse sun gear 10 throughthe rear clutch 7 and is further transmitted to the gear 19 of theoutput shaft 18 through the pinions 15, 16 and 17, thereby reversing theoutput shaft 18.

So far the transmission to which is applied the present invention hasbeen described and next the hydraulic circuit to which is applied thepresent invention will be described with reference to FIGS. 3-7. Ingeneral the hydraulic pressure circuit comprises a hydraulic pressuresource and an actuating circuit comprising a manual shift valve (manualshift range setting valve) 120, an l-2 shift device 130, a 2-3 shiftdevice 135, a check valve 140 and hydraulic lines or conduits. Thehydraulic pressure source 100 comprises an oil pump 101, an oil strainer102, a pressure adjustment valve- 80, a relay valve 90, a check valve103 and an oil cooler 104. The hydraulic pressure source 100 also servesto supply oil to the torque-converter, lubricant to the gear and pinionsand oil under pressure to the actuating circuit 1 10.

The manual valve is coupled to a shift lever (not shown) disposed nearthe drivers seat, and has six positions, P, R, N, D, II and L. When themanual valve 120 is in the N position as shown in FIG. 3, the conduit121 is closed while the valve'chambers 122 and 123 are opened. When themanual valve 120 is in the D position as shown in FIG. 4, the hydraulicconduit 121 is made in communication with. the hydraulic conduits 124,125 and 126. The conduit 124 is directly coupled to a front clutchservochamber 6a; the conduit 125, to the actuating side 22a of the frontbrake band through the l-2 shift device 130; and the conduit 126, to arear clutch servo chamber 7a and to a front brake releasing side 22bthrough the 2-3 shift device 135 and the check valve 140. t

The l-2 shift device 130 comprises a valve 131 and a solenoid 132 andone end of the valve 131 (the right end in the figures) is made incontact with a'rnoving core 133 of the solenoid 132. When the solenoidis not energized the valve 131 is positioned in the right position underthe force of a spring 131 which contacts the valve 131 at the other end(left end) thereof so that the conduits 125 and 134 are communicatedwith each other, whereby the front brake band 22 is applied. Whenthesolenoid 132 is energized, the moving core 133 causes the valve 131 tomove to the left position so that the conduits 125 and 134 aredisconnected. The conduits 134 and 127 are intercommunicated to drainthe conduit 134 so that the front brake band 22 is released. I

Similarly the 2-3 shift device 135 comprises a valve 136 and a solenoid137. One end (the right end in the figures) of the valve 136 is made incontact with the moving core 138 of the solenoid 137. When the solenoidis de-energized, the valve 136 is positioned to the right under theforce of the spring 136 at the other (left) end of the valve 136 so thatthe conduits 126 and 139 are intercommunicated, whereby the check ball141 of the check valve 140 is pressed against the conduit 128, therebyclosing it. The conduits 139 and 142 are intercommunicated so that therear clutch 7 is actuated while the front brake band 22 is released.When the solenoid 137 is energized, the valve 136 is moved to the leftso that the conduits 126 and 139 are disconnected from each other whilethe conduit 139 is communicated with the discharge port 139a.Consequently the pressure in the hydraulic conduit 139 is released.Firstin D range: Both of the solenoids 132 and 137 are energized andonly the front clutch'6 is actuated by the line pressure in the conduit124 of the manual valve 120. When driven from the engine side, theone-way brake 23 is engaged to lock the carrier 13, whereby the firstspeed is attained. In this case, the power is not transmitted from theoutput shaft and the free wheeling condition is maintained.

Second in 'D range: The line pressure in the conduit 124 to the frontclutch 6 is maintained while the solenoid 132 of the l-2 shift device isde-energized so that the conduits 125 and 134 are communicated with eachother, thereby actuating thefront brake-band 22. Thus the second speedisattained.

Third in D range:(See FIG. 4) The solenoid 137 of the 2-3 shift deviceis also de-energized so that the conduits 126 and 139 arecommunicatedwith eachother thereby actuating the rear clutch 7 whilereleasing thefront brake band 22. Thus, the third speed is attained.

II range: (See'FIG. 5) Theline pressure in the conduit 126 to the 2-3shift valve 135is released while only the conduits 124 and 125 arecommunicated with the hydraulic pressure source.ln thiscase,irrespective of the energization or dc-energization of the 2-3 shiftsolenoid 137,'the third speed will not be attained. De-

pending upon the energization or de-energization of the 1-2 shiftsolenoid 132, the first or second speed is attained.

L range: The line pressure in the conduits 125 and 126 is released whilethe conduits 124 and 127 are communicated with the hydraulic pressuresource. In this case, the valve 131 is positioned to the right when thesole noid 132 is de-energized (See FIG. 6) so that the conduits 127 and127' are communicated with each other, whereby the rear brake band 21 isapplied. In consequence both of the front clutch 6 and the rear brakeband 21 are actuated so that the first speed is attained. In this-case,this first speed is different from that in the D range in that the rearbrake band 21 is applied, so that the power from the output shaft may betransmitted, whereby the engine brake or hill braking is applied. Whenthe solenoid 132 is energized (see FIG. 7), the valve 131 is moved tothe left so that the conduits 127 and 134 are intercommunicated whilethe conduit 127' is communicated with the discharge port 134a. Inconsequence the front brake band .22 is applied while the rear brakeband 21 is released, whereby the second speed is attained.

R range: The line pressure in the conduits 124, 125 and 126 is releasedwhile the conduits 127 and 128 are communicated with the hydraulicpressure source so that the rear clutch 7 and the rear brake band 21 areactuated. Thus, the reverse is attained.

So far the hydraulic-pressure circuit to which is applied the presentinvention has been described and next the pressure regulator valve andthe relay valve 90 to which is directed the present invention will bedescribed hereinafter.

The pressure regulator valve 80 has a function of regulating the linepressure PL to be applied to the servos of the front and rear clutches 6and 7 and front and rear brake bands 21 and 22. First the constructionof the pressure regulator valve 80 will be described. The valve spool 81of the valve 80 has five lands 81a, 81b, 81c, 81d and 81e in the ordernamed from the upper end to the lower end as shown in FIG. 3. The valve80 is provided with six oil pressure chambers 82, 83, 84, 85, 86 and 87.The oil pressure chamber 82 is communicated with the conduit 99 from therelay valve 90 to be described in more detail hereinafter. The diameterof the land 81a is larger than that of the land 81b so that the linepressure forced into the oil pressure chamber 82 exerts the upward forceupon the spool 81 because of the land diameter difference. The oilpressure chamber 83 is communicated with the circulating conduit to thetorque-converter while the oil pressure chamber 84 is communicated withthe discharge or pressure conduit 121 of the oil pump 101. Both of theoil pressure chambers 83 and 84 are intercommunicated when the land 81bis in its upper position so that the line pressure in the oil chamber 83is transmitted to the oil pressure chamber 84. The oil pressure chamber85 is in communication with the sump or discharge conduit 89 and iscommunicated with the oil pressure chamber 84 when the land 81c is inits upper position so that the oil'in the oil chamber 84 may be drainedintothe sump (not shown) through the oil chamber 85 and the sump conduit89. The oil pressure chamber 86 is in communication with the conduit 134from the l-2 shift valve 131 through'the conduit 134'. I

The diameter of the land 81d is larger than that of the land 8le so thatthe line pressure transmitted to the oil pressure chamber 86 may exertthe upward force upon the spool 81. The chamber 87 is an empty space.

A coiled spring 106 is loaded between the upper surface of the land 81aand the wall 88 so that the valve spool 81 may be normally biaseddownwardly. The oil pressure is regulated in the pressure regulatorvalve 80 by the equilibrium between the downward force exerted by thecoiled spring 106 and the upward force exerted to the valve spool 81 inthe oil chambers 82 and 86. Thus the regulated line pressure PL existsin the conduit or line 121 and is distributed into the selected conduitsin response to the actuation of or position of the manual valve 120.

Next the relay valve 90 will be described which has a function ofproducing the pressure difference in line pressure PL or differentpressures in response to the position of the manual valve 120. As viewedfrom FIG. 3, the relay valve 90 is provided with four oil pressurechambers 92, 93, 94 and 95. The oil pressure chambers 92 and 94 are incommunication with the oil pressure chamber 82 of the pressure regulatorvalve 80 through the conduit 99. The oil pressure chamber 93 is incommunication with the manual valve 120 through the conduit 126, whichis also communicated with the 2-3 shift valve 136 and in which existsthe line pressure PL only when the manual valve is in D position. Theoil pressure chamber 95 is in communication with the oil pressurechamber 84 into which is directly supplied the oil under pressure fromthe oil pump 101. Under the force of a coiled spring 96 which contacts,to the upper end of the spool 91 of the relay valve 90 the valve spool91 is normally biased downwardly. When the valve spool 91 is in itslower position, the oil chambers 93 and 92 are communicated with eachother so that the line pressure from the manual valve 120 through theconduit 126 is transmitted to the oil pressure chamber 82 of thepressure regulator valve 80. Upon the upward displacement of the valvespool 91, the oil pressure chamber 93 is disconnected from the oilchamber 92 while the oil pressure chambers 95 and 94 are communicatedwith each other so that the line pressure is transmitted to the oilchamber 82 of the pressure regulator valve 80. In this case, the weak orlow line pressure'is produced under the force of the spring 96 as willbe described in more detail hereinafter. It is seen that depending uponthe upper or lower position of the valve spool 91, the different oil orline pressure is produced and transmitted into the oil pressure chamber82 of the pressure regulator valve 80.

The line pressure control operation by the combination of the pressureregulator valve 80 and the relay valve 90 of the types described abovewill be described in detail depending upon the position of the manualvalve 120.

D range: (See FIG. 4)

The oil under pressure from the oil pump 101 is transmitted into the oilpressure chamber 93 through the conduits 121 and 126. The line pressurefrom the w spool 91 together with the force of the coiled spring 96. Theline pressure transmitted into the oil chamber 95 of the relay valve 90from the pressure regulator valve exerts the upward force upon the valvespool 91, but the line pressures acting upon the upper and lower ends ofthe spool 91 are equal so that the downward force exerted by the coiledspring 96 acts upon the valve spool 91 of the relay valve to move itdownwardly. In consequence, the line pressure discharged from the oilpump 101 exerts the upward force upon the valve spool 81 in the oilchamber 82 of the pressure regulator valve 80. When the solenoid 132 ofthe l2 shift valve is de-energized, the l2 shift valve 131 is moved tothe right so that the conduit 125 is communicated with the conduit 134so that the line pressure is transmitted to the oil pressure chamber 86of the pressure regulator valve 80 through the conduit 134'. The linepressure in the oil pressure chamber 86 exerts the upward force on thevalve spool 81 of the pressure regulator valve 80. The line pressure PLgenerated in the pressure regulator valve 80 is a constant low linepressure PLD determined by the equilibrium between the force of thecoiled spring 106 acting upon the upper end of the valve spool 81 of theregulator valve 80 and the oil pressure acting upon the area differencebetween the lands 81a and 81e of the valve spool 81 in the oil pressurechambers 82 and 86.

When the solenoid 132 of the l2 shift valve 131 is energized, the latteris moved to the left position so that the conduit 134 is communicatedwith the conduit 127 and drained. The oil pressure chamber 86 of thepressure regulator valve 80 is also released so that the line pressureproduced in the pressure regulator valve 80 is determined by theequilibrium between the force of the coiled spring 106 and the oilpressure acting upon area difference between the lands 81a and 81b ofthe valve spool 81 in the oil pressure chamber 82. In this case the linepressure is a constant high pressure PHD. In summary in the D range ofthe manual valve 120, the pressure regulator valve 80 produces therelatively high hydraulic pressure or line pressure PHD when the l2shift valve is in its left position (the first speed position) and therelative low hydraulic pressure or line pressure PLD when the l2 shiftvalve is in its right position (second and third speed position). Thehydraulic or line pressure characteristic curves in the D range areillustrated in FIG. 8, from which it is seen that when the shift throughthe speeds from first to second takes places as the rotational speed ofthe output shaft (that is the speed of the car) is increased, therelatively high hydraulic pressure PHD is stepped down to the lowconstant line pressure PLD. The so-called l2 shift point where the firstspeed is shifted to the second speed is varied in response to theengine-torqueresponse signal so that the step-down points of thehydraulic or line pressure are varied as shown in FIG. 8 in response tothe engine-torque-response signals.

II or L range:

' The hydraulic pressure in the conduit 126 from the manual valve isreleased so that in the oil pressure chamber 82 of the pressureregulator valve 80 acts the pressure PMO (to be referred to as thereducing pressure hereinafter) which is equal to the hydraulic pressuresupplied from the oil pump 101 minus the hydraulic pressurecorresponding to the force of the coiled spring 96. More specificallywhen the hydraulic pres sure in the upper oil pressure chamber 93 of therelay valve 90 is exhausted, the valve spool 91 is caused to moveupwardly because of the hydraulic pressure in the oil chamber 95 whichis normally supplied from the oil pump 101, so that the oil chambers 95and 94 are intercommunicated, thereby transmitting the hydraulicpressure to the upper oil chamber 92 of the relay valve 90. Thehydraulic pressure transmitted into the oil in the lower oil chamber 95.As described above, the

downward force is made up of the hydraulic pressure and the force of thecoiled spring 96. so that the downwardly acting hydraulic pressure maybe reduced by a degree corresponding to the force of the spring 96. Thatis, the hydraulic pressure in the oil chamber 92 may be lower than thatin the oil pressure chamber 95 by a pressure corresponding to the forceof the coiled spring 96. This hydraulic pressure is transmitted into theoil chamber 82 of the pressure regulator valve 80. In this case, the oilpressure chamber 93 serves as the sump conduit, the oil under pressureis drained into the oil chamber 93 from the oil chamber 92 in theequilibrium action described above, thereby accomplishing the controlaction.

The oil under pressure is supplied into the conduit 125 when the manualvalve 120. is in II position and into the conduit 127 when the manualvalve 120 is in L position so that depending upon the positions of thel-2 shift valve 131, the hydraulic pressure acts or does not act in theoil chamber 86v of the pressure regulator valve 80 through the, conduit134'. When the hydraulic pressure is transmitted into the oil chamber86, the hydraulic or line pressure produced by the pressure regulatorvalve 80 becomes a lower constant hydraulic pressure PLL which isdetermined by the force of the coiled spring 106, the reducing pressurePMO in the oil chamber 82 and the hydraulic pressure in the oilhydraulicor line pressure produced by'the pressure.

regulator valve 80 is the high constant hydraulic pressure PHL.

In the II or L position of the manual valve 120, the constant highhydraulic pressure PI-IL is produced in the first speed while therelatively low constant pressure PLL, in the second speed. In P, R and Npositions, the constant high hydraulic pressure PHL is generated. Thehydraulic pressurecharacteristic curves depending upon the positions ofthe manual valve, 120 are illustratedjn FIG. 9, which is similar to FIG.8. From both of FIGS. 8 and 9,. the control hydraulic pressure isstepped down at the shift through the speeds from first to second. Themagnitude of the control hydraulic pressure in FIG. 9 are higher. thanthose in FIG, 8 and the hydraulic pressure difference is producedbetween the D position and other positions for examplell or L positionof the manual valve 120. The pressure difference is produced because thehydraulic pressure in the oil chamber 82 of the pressure regulator valveis different depending upon the position of the manual valve. This willbe described in more detail hereinafter. In the D position of the manualvalve 120, the hydraulic pressure as-discharged-from-the oil pump 101 issupplied into the oil chamber 82 of the pressure regulator valve 80 soas to oppose to the force of the spring 106. However, in the positionfor example II or L of the manual valve 120 except the D position, thehydraulic pressure whose magnitude is reduced by a pressurecorresponding to the force of the coiled spring 196 by the relay valveis supplied so as to oppose the force of the: spring 106. The hydraulicpressure supplied into the oil chamber 82in II or L position is lowerthan that in the D position so that the pressure differencecorresponding to that between two positions is shown in the graph ofFIG. 9.

In the present invention, depending upon the position of the manualvalve the hydraulic or line pressure PL having a different magnitude maybe derived and the hydraulic pressure diagram in which the step-downoccurs by the shift through the speeds from first to second, is alsoobtained. Therefore, when the car speed 7 is low, the line pressuredetermined in consideration of the torque increase in thetorque-converter may be supplied to the hydraulic servo chambers of theclutches and brake bands,'thereby producing the sufficient engaging orlocking forces. On the other hand, when the car speed is increased, thetorque-converter is held in coupling or almost coupling position sothatno torque increase is produced; In this case, the low constant linepressure is supplied to the hydraulic servos so as to prevent the powerloss due to the oil pump loss or the like. Especially the controlhydraulic pressure is varied by the relay valve 90 in the D and otherranges so that the sufficientand suitable hydraulic pressures may beappliedto the rear clutch 7 and to the rear brake band 21 when reversed.To change the traveling condition, when the car is started at the secondspeed in the II range, the hydraulic pressure slightly higher than thatat thesecond speed in the D range is supplied so as to increase thetorque in the low-speed range. In addition, as the means for varying thecontrol hydraulic pressure depending upon the traveling conditions, the

shift valves for shift control are used so that the valve means forvarying the hydraulic pressure may be eliminated, thus resulting in thesimple hydraulic circuit.

In the preferred embodiment described hereinabove, the conduit 134 fromthe l-2 shift valve to the servo is communicatedwiththe oilpressurechainber 86 of the pressure regulator valve 80 so that the linepressure may be stepped down simultaneously when-the secondis selected.However, it is to.be understood that the conduit139 from the 2-3 shiftvalve to the servo may be communicated with the oil chamber 86 of thepressure regulator valve 80 so thatthe line pressure may be stepped downsimultaneously when the ,third is selected.

As described hereinabove, l-2.shif t valve 131 and the 2-3 shift valve136 are actuated in order to vary the pressure regulating operation ofthe pressure regulator valve 80, thereby accomplishing the automatictransmission. This is done whether the solenoids 132 and/or 137 areenergized or de-energized.

The shift control due to the energization and deenergization of thesolenoids 132 and/or 137 may be effected depending upon the travelingconditions.

Various shift control systems have been proposed, for example, in US.Pat. Nos. 3,068,715 and 3,019,666. However, another novel shift controlsystem will be developed, but it is to be understood that the presentinvention may also be applied to a newly developed shift control systemwithin the scope of this invention.

The description has been so far directed to the threeforward-speeds andone-reverse-speed automatic transmission, but various variations andmodifications may be effected without departing from the scope of thepresent invention if the state of the art of the present invention issufficiently understood. This is also clear from the fact that thepresent invention has many technical features.

What is claimed is:

1. In a hydraulic pressure control device for use in an automatictransmission of the type including a fluid torque-converter or fluidcoupling and a transmission provided with hydraulic servo means forbrake bands, clutches and the like which carry out an automatic speedchange: an oil pump for generating the hydraulic pressure to be suppliedto said hydraulic servo means, a pressure regulator valve forcontrolling the hydraulic pressure to be applied to said hydraulicservo, said pressure regulator valve having an oil pressure chamberformed therein for controlling said hydraulic pressure, a manual valvehaving at least two positions, a relay valve for supplying a requiredhydraulic pressure to said oil pressure chamber in said pressureregulator valve, a first conduit for communicating said oil pump withsaid relay valve when said manual valve is in one position, and a secondconduit for communicating said oil pump with said relay valve throughsaid manual valve when said manual valve is in another position, saidrelay valve having a movable valve element and a spring urging saidvalve element, said relay valve supplying a reduced hydraulic pressureto said oil pressure chamber in said pressure regulator valve when saidmanual valve is in one position which reduced pressure is equal to thehydraulic pressure supplied from said first conduit minus the pressurecorresponding to the force of said spring, while when said manual valveis in another position said relay valve supplying the hydraulic pressuresupplied from said second conduit and being subjected to no regulationto said oil pressure chamber in said pressure regulator valve, and thehydraulic pressure control operation of said pressure regulator valvebeing varied in response to the positions of said manual valve.

2. A hydraulic pressure control device for use in an automatictransmission as defined in claim 1 characterized by further including asecond oil pressure chamber formed in said pressure regulator valve forcontrolling the hydraulic pressure to be supplied to said hydraulicservo means, an electrically operated automatic shift valve activated inresponse to a transmissionactuation si nal for selectively supplying toand discharging rom said hydraulic servo means the hydraulic pressurethereby establishing a low-speed forward-drive ratio and a high-speedforward-drive ratio, and a third conduit for communicating the conduitfor supplying the hydraulic pressure from said automatic shift valve tosaid hydraulic servo means with said second oil pressure chamber in saidpressure regulator valve, the control operation of said pressureregulator valve being varied in response to the position of said manualvalve and the actuation of said automatic shift valve. 1 I

1. In a hydraulic pressure control device for use in an automatictransmission of the type including a fluid torqueconverter or fluidcoupling and a transmission provided with hydraulic servo means forbrake bands, clutches and the like which carry out an automatic speedchange: an oil pump for generating the hydraulic pressure to be suppliedto said hydraulic servo means, a pressure regulator valve forcontrolling the hydraulic pressure to be applied to said hydraulicservo, said pressure regulator valve having an oil pressure chamberformed therein for controlling said hydraulic pressure, a manual valvehaving at least two positions, a relay valve for supplying a requiredhydraulic pressure to said oil pressure chamber in said pressureregulator valve, a first conduit for communicating said oil pump withsaid relay valve when said manual valve is in one position, and a secondconduit for communicating said oil pump with said relay valve throughsaid manual valve when said manual valve is in another position, saidrelay valve having a movable valve element and a spring urging saidvalve element, said relay valve supplying a reduced hydraulic pressureto said oil pressure chamber in said pressure regulator valve when saidmanual valve is in one position which reduced pressure is equal to thehydraulic pressure supplied from said first conduit minus the pressurecorresponding to the force of said spring, while when said manual valveis in another position said relay valve supplying the hydraulic pressuresupplied from said second conduit and being subjected to no regulationto said oil pressure chamber in said pressure regulator valve, and thehydraulic pressure control operation of said pressure regulator valvebeing varied in response to the positions of said manual valve.
 2. Ahydraulic pressure control device for use in an automatic transmissionas defined in claim 1 characterized by further including a second oilpressure chamber formed in said pressure regulator valve for controllingthe hydraulic pressure to be supplied to said hydraulic servo means, anelectrically operated automatic shift valve activated in response to atransmission actuation signal for selectively supplying to anddischarging from said hydraulic servo means the hydraulic pressurethereby establishing a low-speed forward-drive ratio and a high-speedforward-drive ratio, and a third conduit for communicating the conduitfor supplying the hydraulic pressure from said automatic shift valve tosaid hydraulic servo means with said second oil pressure chamber in saidpressure regulator valve, the control operation of said pressureregulator valve being varied in response to the position of said manualvalve and the actuation of said automatic shift valve.